From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 4E36530C63A; Wed, 28 Jan 2026 15:52:07 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769615527; cv=none; b=kBz8Wo53JLfMf/5G03h1orC/me/FfT115aASesbbJubJbxKT0Yb9jW6ldhKHW5ygOYziDHKdGuCTmD4qjKYa/X6gVnXNzvnMKugsiM4AdY2SJ9VPtNN1C6bsTAF20p7lSPGdASlK84GXeRg7fxlaOxGuZnJILJmq8i7J+47oDyI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1769615527; c=relaxed/simple; bh=67kT40TUbe0KV3MGrshwjGJDIfgBsmnyIv64CZ7jEM0=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=eHaIuDNnBkNFjoyepoNVN928vFGkgtqHsGz+1BAs3xwbnQ5/g8kvgN4SZejKRHwTLmBA9SwQJISV86WNCaieO8TtDCtUv7JOMg8mKoTrRBHp8rx1pLTWZpwmerGtX9uLn4GxGbQr1BmAkfLas+xX2NHxHT6fWVVQQryAtWJ/bxM= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=YOqyDpFC; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="YOqyDpFC" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 13E90C4CEF7; Wed, 28 Jan 2026 15:52:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769615527; bh=67kT40TUbe0KV3MGrshwjGJDIfgBsmnyIv64CZ7jEM0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=YOqyDpFCOW1PHiL4LGoLxV9m13/Y3Hrntsen+74EkeKdh1CBMOv2SPGn8rkcKsx51 g+pzYheWs2rb3CtRUrSEn9f2IXqypMOlCDZQT3f9WIKLoBBgTfteNadlJjEGQr+D4d oopCjh+U4aXtJkIMfHDIrWFrSc64tDDXQVWLrHGj/hIZjmU0TXsA7Ux2wPccII6FbV xFyhDnhvGi66/cZhSTMPiyqfBcwDbW56UL/KoX/M4DAUk/rLvNymqjJM0MO0Eg9Dsk 5G62q4J75rdHUSS1IQ9xjG9nmOaeBfGCCLrxEsvHvdFU0LAAdk919OP8e2KQRBsy0E XbTZLvYUFTTnQ== Message-ID: Date: Wed, 28 Jan 2026 16:52:01 +0100 Precedence: bulk X-Mailing-List: linux-input@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v13 1/3] dt-bindings: i2c: Add CP2112 HID USB to SMBus Bridge To: Conor Dooley , Andy Shevchenko Cc: Danny Kaehn , Rob Herring , Krzysztof Kozlowski , Benjamin Tissoires , Andi Shyti , Conor Dooley , Jiri Kosina , devicetree@vger.kernel.org, linux-input@vger.kernel.org, Dmitry Torokhov , Bartosz Golaszewski , Ethan Twardy , linux-i2c@vger.kernel.org, linux-kernel@vger.kernel.org, Leo Huang , Arun D Patil , Willie Thai , Ting-Kai Chen References: <20260127-cp2112-dt-v13-0-6448ddd4bf22@plexus.com> <20260127-cp2112-dt-v13-1-6448ddd4bf22@plexus.com> <20260127160217.GA3776731@LNDCL34533.neenah.na.plexus.com> <20260128-magnificent-faithful-otter-c4f900@quoll> <20260128-pelican-silenced-cd6a5bf69672@spud> From: Krzysztof Kozlowski Content-Language: en-US Autocrypt: addr=krzk@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 8bit On 28/01/2026 16:06, Conor Dooley wrote: > On Wed, Jan 28, 2026 at 02:49:39PM +0200, Andy Shevchenko wrote: >> On Wed, Jan 28, 2026 at 11:35:25AM +0100, Krzysztof Kozlowski wrote: >>> On Tue, Jan 27, 2026 at 10:02:17AM -0600, Danny Kaehn wrote: >>>> On Tue, Jan 27, 2026 at 08:47:48AM -0600, Danny Kaehn wrote: >>>>> This is a USB HID device which includes an I2C controller and 8 GPIO pins. >>>>> >>>>> The binding allows describing the chip's gpio and i2c controller in DT, >>>>> with the i2c controller being bound to a subnode named "i2c". This is >>>>> intended to be used in configurations where the CP2112 is permanently >>>>> connected in hardware. >>>>> >>>>> Signed-off-by: Danny Kaehn >>>>> --- >>>> >>>> Hi Folks (Intended for Rob or Krzysztof), >>>> >>>> Wasn't sure the best way to go about this, but trying to see the best >>>> way to get a message in front of you regarding an ask from Andy S. >>>> >>>> In [1], Rob H initially directed that the gpio chip share a node with >>>> the CP2112 itself, rather than having a subnode named 'gpio'. >>>> >>>> Initially, I did the same thing for both DT and ACPI, but Andy S. >>>> directed that ACPI should not have the node be shared in that way. >>>> >>>> With the last revision of this patch, Andy S. asked that I try to get a >>>> rationalle from Rob (or other DT expert presumably) on why the gpio node >>>> should be combined with the parent, rather than being a named subnode >>>> [2]. >>> >>> Because it is explicitly asked in writing bindings. Please read it. >>> >>> Because we do not want Linux driver model affecting design of bindings >>> and DTS, by subnodes present only to instantiate Linux drivers. I do not >>> care about driver model in this review and I do not see any reason it >>> should make DTS less obvious or readable. >>> >>> That's actually rule communicated many times, also documented in writing >>> bindings and in recent talks. >> >> Does DT represents HW in this case? Shouldn't I²C controller be the same node? >> Why not? This is inconsistent for the device that is multi-functional. And from >> my understanding the firmware description (DT, ACPI, you-name-it) must follow >> the HW. I don't see how it's done in this case. > > The i2c controller should probably be in the same node too, unless it > would cause conflicts between function (e.g. inability to figure out if This one is the rationale. > a child is a hog or a i2c device). I would like a rationale provided for > why the i2c controller is in a subnode. I2C controller will have children, because it is a bus, so moving it up one level would make the entire node I2C bus and that's not only problem for the kernel but actually for reading DT - we expect consistent choice for children, instead of mixing nodes with and without bus-addressing. What's more, if you have two buses you also need separate nodes to group them (obviously). Best regards, Krzysztof